1. Field of the Invention
This invention relates to an improvement of a noncontact type tonometer, in which fluid is discharged to the cornea of an eye to be tested to transfigure and an intraocular pressure is measured with reference to the transfiguration of the cornea.
2. Description of the Prior Art
Heretofore, in a noncontact type tonometer, an adjustment of the position of a measuring optical system of an apparatus body in the vertical direction and in the right and left direction with respect to an eye to be tested and an adjustment of a working distance between the eye and a nozzle for discharging a fluid toward the eye are performed as a verification of alignment. As such a noncontact type tonometer, there is one of the type in that an alignment target ray of light is projected to the eye to be tested from the axial direction of a nozzle in order to verify the alignment. This kind of noncontact type tonometer, when the alignment has been completed, projects a fluid such as an air pulse, etc. toward the eye in order to transfigure the cornea of the eye to be tested and measures the intraocular pressure (for example, Japanese patent publication No. Sho 56-6772).
However, this type of a conventional noncontact type tonometer is constituted as such that a total observation of the anterior portion of the eye to be tested is unavailable. Therefore, there is such an inconvenience as that the inspector cannot recognize the state of the eye to be tested during the period from the alignment verification till the completion of the fluid discharge. Therefore, if, for example, the discharging of the fluid should be started when the eye lid is closed, a value of an intraocular pressure obtained would be unreliable.
Also, in this kind of noncontact type tonometer, an alignment target ray of light, when the alignment is proper, is made incident to the cornea of the eye to be tested from the perpendicular direction and a virtual image is formed in the center of curvature by the alignment target ray of light. And, this virtual image is reimaged on a reticle plate and based on the sharpness of the virtual image formed on the reticle plate and the position of the virtual image formed on the reticle plate, the properness of the alignment is determined. Therefore, it is difficult for the inspector to determine the properness of the alignment correctly and rapidly.